Recommended IDE...?

Looking to try using an Integrated Development Environment.
Is there an industry standard everyone uses and I should get familiar with,
or will any do?
My previous experience is with NotePad and TextWrangler.
I've Windows98SE and OSX 10.5.8 [Leopard] ;-), and use both in tandem via a
KVM switch, XD.
Thanks in advance, =).
Yours,
Andrew.